Abstract: This study demonstrated the use of metallographic analysis and NIST’s Fire Dynamics Simulator (FDS) program to identify the cause of an actual electrical fire. A severely carbonized steel plate and a cable with a bead were found inside a damaged switchboard from the debris of a factory fire. By metallographic analysis, the copper spatter on the steel plate was found to imply a short circuit has occurred and that this was the probable ignition source of the fire was supported by the presence of a small amount of copper oxide and by the cavities with the tree-like grain microstructures in the bead. The heat estimated to have been released per unit area of the switchboard in question (approximately 236.29 MJ/m2) served as key input data for applying the FDS simulation of the blaze. The simulation indicated that thermal insulation polyethylene (PE) played an important role in the rapid fire spread.